Digital brushes are different than real world brushes. In the SketchClub app you can design a brush as a stamp or as an element that can be manipulated many different ways. Using a simple image, you can create natural elements in an image. All the grass and other vegetation in my past images started as brushes I made myself. Here is a kinda leafy brush.

It is not just how good your brush looks but how you use it. There are brush controls that allow you to stroke it onto the canvas lots of different ways. The left example is a scatter stroke. Best used for texturing. The middle is an even stroke spaced out a bit. Maybe a necklace. Also note that there is a taper to the stroke. There are lots of other ways to affect how the stroke looks. The one on the right has the brush elements touching each other. Does it look like anything?